Proteoglycans will be isolated from normal human and rabbit lung parenchymal and tracheobronchial tree tissue using dissociative extraction with 4 M guanidine hydrochloride in the presence of protease inhibitors and purified in isopycnic cesium chloride gradients. Characteristics of the proteoglycans isolated from samples of different ages are to be compared. Parameters to be compared include size and heterogeneity, amino acid and carbohydrate composition, glycosaminoglycan structure and content and the possible presence of glycopeptides in the isolated proteoglycans. The proteoglycans will be investigated immunologically to determine histologic localization within the lung and immunologic relatedness of the core proteins of the isolated fractions to other proteoglycans such as the aggregating proteoglycan complex found in hyaline cartilage. Studies with lung organ culture and isotopic precursors such as 35S-sulfate and 3H-serine will be used to study the biosynthesis of these macromolecules in vitro.